1. Field of the Invention
The present invention relates to musical instruments. More particularly, the present invention relates to a structural, suspended torsion brace for use in acoustic musical instruments, such as archtop guitars.
2. Discussion of Related Art
Hollow body guitars, such as archtop guitars, are well known. FIG. 1 illustrates the body 100 of a typical archtop guitar; FIG. 2 is a side cutaway view of the body 100. In a hollow body guitar, sound is generated by the vibration of strings connected to a bridge 102. The bridge 102 is connected to the hollow body 100. To aid in the generation, amplification, and projection of the sound made by the string vibration, the hollow body 100 includes a chamber which is typically defined by an upper plate 104, to which the bridge 102 is connected, a lower plate 106 (see FIG. 2), and a side 107. The upper and lower plates 104, 106 are connected to side 107. In an archtop guitar as seen in FIGS. 1 and 2, the upper plate 104 is slightly arched. The upper 104 and lower plates 106 vibrate in response to the vibration of strings 108 (for simplicity of illustration, the strings are only seen in FIG. 2). One or more sound holes 110 may be provided to project the sound from the chamber.
To generate sound, the strings 108 are kept taut and may be depressed along a fret board 112 (partially seen in FIGS. 1 and 2) to adjust the strings"" length and thus the frequency of the vibration when a string is plucked or strummed. The fret board 112 is connected to the front, or head, of the guitar body 100. The strings 108 are connected to the bridge 102, which transfers the vibrations of the string to the hollow body. The strings 108 may also be anchored by a tailpiece 114, which is typically connected to the end, or heel, of the guitar body 100. Because of the pressure placed on the guitar body from the taut strings, one or more rigid braces 116 are typically glued to the upper plate 104 and/or lower plate 106 of the guitar body. Blocks 118, 120 may be placed at the head and heel to provide support to the body.
Hollow body guitars suffer from several drawbacks. One major drawback associated with amplified hollow body guitars is feedback. During a performance, the amplified sound of the guitar may vibrate the upper and/or lower plates 104, 106. Because these vibrations are the amplification of the sound generated by the guitar, the result is feedback, which when uncontrolled, is undesirable. Note that solid body guitars (i.e., guitars in which the body is a solid piece of wood or other material) do not suffer from the feedback problem to the same extent as hollow body guitars.
Several solutions to the feedback problem in hollow body guitars have been proposed. One solution is to make the upper and/or lower plates thicker. A second solution is to remove the sound hole. A third solution is to add more bracing to the upper and lower plates. All of these solutions tend to dampen the vibration of the plates. Although these solutions do minimally reduce feedback, because they dampen vibration they also adversely affect the guitar""s sound, projection, and sustain (the amount of time a note will sound).
Therefore, it is an object of the present invention to provide an improved acoustic musical instrument which decreases feedback.
It is a further object of the present invention to provide a torsion brace which does not dampen the vibrations of the plates.
These and other objects of the present invention are provided by an acoustic instrument having a structural torsion brace according to the present invention. In a preferred embodiment of the present invention an acoustic instrument is provided with a torsion brace which contacts the upper and lower plates in only three locations. The first location is at the head of the body, the second is at the heel of the body, and the third is where the bridge connects to the upper plate.
This arrangement provides structural support to the guitar body because it braces the head and heel of the body and also supports the upper plate where the bridge connects to it. However, because the brace contacts the plates only at its head, heel, and bridge, the plates may vibrate freely. This structure has been shown to resist feedback, yet does not dampen the vibration of the plates. As a result, the sound, projection, and sustain of the guitar are not adversely affected.